Atmospheric Autoxidation of Organophosphate Esters

Zihao Fu, Hong Bin Xie*, Jonas Elm, Yang Liu, Zhiqiang Fu, Jingwen Chen

*Corresponding author for this work

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaperJournal articleResearchpeer-review

Abstract

Organophosphate esters (OPEs), widely used as flame retardants and plasticizers, have frequently been identified in the atmosphere. However, their atmospheric fate and toxicity associated with atmospheric transformations are unclear. Here, we performed quantum chemical calculations and computational toxicology to investigate the reaction mechanism of peroxy radicals of OPEs (OPEs-RO2), key intermediates in determining the atmospheric chemistry of OPEs, and the toxicity of the reaction products. TMP-RO2 (R1) and TCPP-RO2 (R2) derived from trimethyl phosphate and tris(2-chloroisopropyl) phosphate, respectively, are selected as model systems. The results indicate that R1 and R2 can follow an H-shift-driven autoxidation mechanism under low NO concentration ([NO]) conditions, clarifying that RO2 from esters can follow an autoxidation mechanism. The unexpected autoxidation mechanism can be attributed to the distinct role of the -(O)3P(•O) phosphate-ester group in facilitating the H-shift of OPEs-RO2 from commonly encountered -OC(•O)- and -ONO2 ester groups in the atmosphere. Under high [NO] conditions, NO can mediate the autoxidation mechanism to form organonitrates and alkoxy radical-related products. The products from the autoxidation mechanism have low volatility and aquatic toxicity compared to their corresponding parent compounds. The proposed autoxidation mechanism advances our current understanding of the atmospheric RO2 chemistry and the environmental risk of OPEs.

Original languageEnglish
JournalEnvironmental Science and Technology
Volume56
Issue11
Pages (from-to)6944–6955
Number of pages12
ISSN0013-936X
DOIs
Publication statusPublished - Jun 2022

Keywords

  • atmospheric oxidation
  • peroxy radicals (RO)
  • quantum chemical calculations
  • secondary organic aerosol (SOA)
  • volatile chemical products (VCPs)
  • Atmosphere/chemistry
  • Phosphates
  • Environmental Monitoring
  • China
  • Esters
  • Flame Retardants/analysis
  • Organophosphates

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